Motion picture printer



May 7, 1940. E. w. KELLO GG MOTION PICTURE PRINTER Filed Feb. 26. 1937 2Sheets-Sheet 1 INVENTOR [DA APO M LLCEG 8Y2 A TORN Y y 1940- E. w.KELLOG G 2.200.086

MOTION PICTURE PRINTER Filed Feb. 26, 1937 2 Sheets-Sheet 2 mxxwInventor ED WARD l/V. KELLOGG (Ittomeg mama May 7, 1940 2,200,086

UNITED STATES PATENT orrlcs MOTION PICTURE PRINTER Edward W. Kellogg,Moorestown, N. J., asslgnor to Radio Corporation of America, acorporation of Delaware Application February 26, 1937, Serial No.127,838 Claims. (01. 95-15) My invention relates to printers and moreparticularly to the type of printer used for the con tinuous printing ofmotion pictures.

Printers, in general, are of one or the other of two types, 1. e., thecontinuous type, wherein both films are moved continuously past theprintlhg point, and the intermittent or step type, where each frame ofthe picture is held stationary for a moment, each picture being printedwhile both jection printer, in which an optically produced image of aportion of the negative is-projected on the positive film, on which theprint is being made. This negative image travels with the positive film,and there should be no relative movement of the image and the film, if aclear sharp print is to result. Continuous projection printing is nowapplied on a commercial scale to sound tracks, with satisfactoryresults, but

films are stationary and the films being then the same principle cannotwell be applied to picmoved to the next frame position. ture printingsince it is important that the frame In the step type of printer theimage remains lines between pictures-shall come directly oppostationaryduring printing, but the machines are site sprocket holes. Themechanical filters emusually rather slow and are quite noisy, the ployedin the sound printers call for considervibration caused by theintermittent feed mochaable tolerance in the longitudinal location of anism greatly limiting the speed of operation, given recorded material,this latitude or tolerance in continuous printers, on the other hand, anamountin i m y cases, to much as a ham equally serious objection arises.In these print an inch. This does no harm in the case 01' a ers, asheretofore manufactured, the film is pulled Sound P past the printingpoint by or over sprockets. For the reason just explained, it ispractically Since motion picture film expands or contracts withvariations in humidity as well as with age, it is impossible to make asprocket which will handle difierent films, i. e., films havingdlfiepent characteristics as to moisture or age, equally satisfactorily.and the departures from uniform motion, or, in other words, movements pithe films relative to each other, result in blurring, it the printingtakes place when the films are both in motion, as is the case withcontinuous printers.

lhroughout this specification, the term megative is used as referring tothe exposed and de veioped film from which a print is to be made and theterm positive is used as referring to the print mode from the negative.However, E do not mean to limit the use or these terms to a photographicnegative Icy using the term negative as referring to the film from whichthe print is made, whether it he an original photoraphic negative, apositive made therei'rom, or a duplicate negative, and the term positiveis likewise used in referring to any print so made.

Inaddition to the classification into continuous and step types,printers are also classified into the contact and projection types, inthe former of which the negative film and positive stock are maintainedin direct physical contact at the printing point, and in the latter ofwhich an image of the negative is projected onto the positive. For themost part, contact printers are of the continuous motion type, whileprojection picture printers are of the step type. It is quite possible,however, to design a continuous pronecessary in the case of a continuouspicture printer (whether of the contact or the projection type) topropel both films through the printing aperture or apertures by means ofsprockets. Any

irregularities of movement due to sprocket tooth action cause relativedisplacements of the two films in contact, in the case of a contactprint er, or relative movements of the negative image and the positivefilm, in the case of a projection printer, in either case giving rise toblurring of the printed picture.

The negative him, since it has already been printed, developed, fixedand dried, is, in general, somewhat shrunken and if it be relativelyold, the shrinkage is much greater than if it were new, and it may evenvary from one end of the reel of-film to the other. The positive filmstock, on the other hand, is usually fairly fresh and it may have beenjust freshly perforated so that the sprocket hole spacings are exactlythe theoretically correct distance.

These variations in film length and film shrinkage cause the sprockethole pitch to fail to coincide' with that of the sprocket teeth, andthere is, accordingly, a slight movement of the films relative to thesprocket and relative to each other as each sprocket tooth leaves theperforation, and the succeeding sprocket tooth takes up the driving ofthe film. So long as a given tooth (or pair of teeth) is pulling thefilm, the linear speed of the latter is .determined entirely by the bodydiameter and speed of rotation of the sprocket, independently of theshrinkage of the film. But the average speed or the film varies withshrinkage, and the diflerences in average speed are taken care 0! bydiflerences in the magnitude of the periodic readjustments, alreadydescribed.

It should be understood that in this specification and also in theappended claims reference to the engagement or disengagement of anytooth may refer, in the case of films having two rov-s of sprocketholes, to any given pair of teeth which operates simultaneously at thetwo edges of the film.

Standard 35 mm. film has 4 sprocket holes per frame or 64 sprocket holesper foot, and if the film is moved continuously the aforesaid slippageof the film from one sprocket tooth to the next causes a slight relativemovement of the films 4 times to each frame. It the print ing apertureis relatively large, these separate blurs are indistinguishable butcause a general lack of definition over the entire area of the print. Ifthe area being printed at any instant is confined to a very narrowrectangle, extending transversely to the film movement, the blur ringeffect or irregularities of motion is reduced, but instead there isdistortion oi the picture, various parts being stretched out orcompressed. The narrowing 01' the printing aperture, which shortens thetime of exposure, is analogous to taking a quick snapshot to avoidblurring when the subject is moving. In any case, it is evident thatwhether a narrow or wide rectangle is printed at a time, the picturequality is injured byany irregularities in movements of the-films whichresult in any displacementoi either film from the position which itideally should occupy at any instant.

In accordance with my invention, I do not.

prevent all irregularities oi motion, ior this is impossible withsprocket propulsion, but 1 confine the eflect oi the irregularities tothe frame lines or spaces between the ictures. This is accomplished inmy improved printer, by printing by means of a narrow line or rectangleof light across the picture, and by using only one sprocket tooth perframe. The sprockets are so oriented in relation 'to the printing pointthat a sprocket tooth leaves the film While the frame line between thepictures is at the printing point, and any slippage oi the film istherefore local ized at the blank irame line without any deleteriousefiect within the area oi the picture itself.

a continuous printer in which blurring is confined to the frame lines,or to aregion so close to the frame lines as to be unobiectionable.

Another object of nrv invention is to provide a type 0! continuousprojection printer which may be used either for enlarging "or reducing.

Other and incidental objects of my invention will be apparent to thoseskilled in the art froma reading or the following specification andinspection of the accompanying drawings in which Figure 1 is adiagrammatical longitudinal sectlon of a projection printer made inaccordance with my invention,

, Figure 2 is a transverse longitudinal section or a projection printertaken on the optical axis along the line 2-2 of Fig. 1, but with thesprockets omitted,

Figure 3 is a vertical section through a contact printer made inaccordance with my invention, and

Figure 4 is a transverse section on the line 1-4 of Fig. 3.

Referring first to Fig. 1, a printing lamp in, which is preferably ofthe coil filament incanpasses through the vertical axis cylindrical lensI i, then through the relatively short focus cylindrical lens l2, whichnarrows the light into a small beam at the point it on the film M. Aslotted mask 15 is provided to prevent stray light from passing throughthe apparatus. This arrangement serves to limit the area being printedat any given instant to a narrow rectangle across the film, but thereare numerous other arrangements of lenses or apertures "which wouldaccomplish the same purpose. An image of the illuminated area at it isfocused by the lens it onto the film W at the point M, where it producesa correspondingly narrow image. The films id and i! are drawn over thesprockets l9 and it at appropriate relative speeds. The lens it is solocated as to reduce (or enlarge) the image in the ratio or frameheights desired, which corresponds to the relative speeds of the twofilms. Thus the image oi the negative, on the surface of film l'l, movesthrough the printing point it at the same speed as the film itself.

In the present instance, the film W is illus trated as a conventional 15mm. film, while the film M is illustrated as the conventional 35 min.film. Although standard 16 mm. film has only one sprocket hole perframe, standard 85 mm. film is provided with four sprocket holes perframe, and all printers at present in use employ sprockets with enoughteeth to engage all of the sprocket holes. In order to perform myinvention, I provide, at the 35 mm. end of the device, only one sprockettooth for-each frame of the picture, and this is so located that whenthe sprocket tooth reaches the roller ll, where the film leaves thesprocket it, the frame line of the picture will be at the point It,thereby localizing at this point any longitudinal slip of the film whichmay occur when this tooth is disengaged and the next tooth begins to dothe pulling. It has already been pointed out that the film speed. duringthe time that ahy one tooth is doing the pulling, is constant,independent oi iilm shrinkage. It is therefore possible to design themachine and its optical system so that the optical ratio will exactlycoincide with the dim speed ratio during this interval.

Asshown in Fig. 2, the cylindrical lens ll serves as a condenser lens todirect the light from the lamp it onto the 11111 picture width oi thehim, and the stop it permits light from this entire width to pass,thereby illuminating the corresponding portion of the width of the film18.

It will be apparent that in the apparatus as described, both films willmove continuously at a uniform speed past a. printing point during theprinting of the entire picture, due to the continuous engagement of thefilm with the particular sprocket tooth which happens to be pulling it.When the sprocket tooth engages or disengages and the dim slips slightlyto adjust itself to the next tooth, the printing aperture is at theframe line and no blur within the picture area occurs.

- descent type, is provided. Light from this lamp M It is desirable tokeep each of the films ll '35 1 over which the film runs, or by a springshoe pressing lightly against the fihn, or any equivalent to. thesedevices. It may be desirable, in order to permit easier readjustment of.the films at the moment of transfer from one tooth to the next, toprovide for a periodic relief of such pressure as may be exerted byrollers II and 55.- This maybe accomplished in the manner here-1,inafter described in connection with the contact printer. Thisrefinement, however, will, in general, not be necessary, for the rollers2| and I5 may be adjusted-to just hold the film against'the body of thesprocket without exerting enough pressure to materially resist thenecessary slipping.

It is, of course, essential that the gearing or the common drivingsystem(not shown) which determines the relative speeds of sprockets i9 and 20shall be of a high order'of accuracy in order that the exact speed ratiomay be maintained throughout the printing of the picture. Since theshrinkage factor does not enter into the operation of the mechanicaldriving system, and the gears may be provided with as large a number ofaccurately fitting teeth as may be necessary, it is not diificult toconstruct a printer in which all inaccuracies due to the driving systemwill be very small compared with those which now resuit from misfitsbetween sprockets and films.

The species of the invention, Figs. 3 and 4, shows a. contact printerwherein the sprocket teeth are withdrawn at appropriate times to permitthe films to slip into engagement with the next succeeding sprocket. Themoment of disengagement of the pulling tooth can be determined by theposition of the stripper or by whatever features of the design cause thefilm to leave the sprocket, but where a single sprocket carriesbothfilms, as in the case with contact printers, the stripping cannot be asaccurately controlled as in the case of separate sprockets. Therefore,in the preferred form of my invention, as applied to contact printers, Iprovide the sprocket with retractable teeth, whereby the moment ofwithdrawal can be accurately detenmined. This measure serves to reducethe width of the slightly blurred area adjacent to the frame lines. InFigs. 3 and 4, the film supporting drum or sprocket is indicatedat 30and is carried upon the shaft 3| which passes through the frame 33 ofthe apparatus. The drum consists of two separated discs, as shown,connected by the hub 32. The frame also carries the shafts 34 and".which, in turn, carryresilient pressure rollers 36, which serve to holdthe films in contact with the drum and with each other, in order toinsure optimum printing. The negative film 31 and the positive filmstock 38 pass over the surface of the drum 30, and light from the source40 is directed by the prismatic lens 40 through the film- 31 to the film34 at the point 4|.

A mask 42 may be provided adjacent the lamp 39 to secure a long narrowline of light transversely of the films, or the filament of the lamp 39maybe in the form of a long thin coil or a straight filament,'in orderto secure this same result.

The drum II is provided with retractable sprocket teeth 44, carried uponsliding bars 44, which are movable in appropriate recesses in the drum30. Each of these slides is provided with a projecting pin 4!, whichextends through the corresponding side of the drum ill and engages theslot in the corresponding stationary cam 48. It will be apparent thatthe contour of the slots in the cams 46 will cause the pins 46, andthere.-' fore the sprocket teeth 43, to move in or out at appropriatepoints during the revolution of the K drum 30. The slot in each of theearns 46 is so contoured that any aligned pair of teeth 43 will engagethe sprocket holes adjacent the point 4| when the line of light at thepoint 4| is at the frame line between picture areas. The next precedingpair of teeth 43, which would then be at the point 41, would besimultaneously withdrawn by the portion 48 of the slot in the cam, andthe tooth adjacent the point 4| would thereby become the sole drivingmember. I

Each film is provided with a pair of shoes 49 and 50, one of which isstationary and the other of which is pressed lightly by a spring, suchas 5|, against the film, thereby frictionally engaging the film andcausing tension to be exerted longitudinally in the film against theaction of the teeth 43 in the drum 30 which at any time tend to pull thefilm downwardly. This insures definite seating of the film against thepulling teeth.

The shaft 3| is provided with a gear 53, shown in Fig. 4, which engagesa gear Men the shaft 34. This gearing causes the resilient rollers 36 tobe so rotated in synchronism with the drum 30 that the transversegrooves in the tires of the roller 36 reach the position adjacent to thesprocket just as the teeth reach the position opposite roller 36. Thisprevents interference between the sprocket teeth and the tires of roller46. v

In addition to the grooves in the tires of roller 86, I have providedfiat spots so positioned that there. is no contact between the tires andthe film at the moment that the readjustment or slipping of the film isdesired. The absence of pressure at this moment permits the film to beretarded slightly by the brakes 49 and 50, so that both films will'slipinto firm engagement with the teeth 43 adjacent to the point 4| Sincethis slipping occurs during the time the frame line is being exposed, noblurring of the picture occurs. The films are then held in fixedrelation to each other by means of the acting sprocket teeth, and areheld firmly together and against the sprocket by the full-thickness partof the tires of the rollers 36, until the entire frame of the picture isprinted as the film moves past the point 4|. When the next succeedingframe line reaches the point 4|, the driving sprocket teeth carrying thefilm will have reached the point 41, and the action will again berepeated.

It will be apparent from the foregoing that in each form of printer Ihave provided a means for permitting the necessary and inevitable slipengagetheiimsaidteethbeingsoarrangodthat 14 only one tooth is adapted toengage the film at a time, means for causing the film to be disengagedfrom the driving toothand engaged by the next succeeding tooth when theframe-line between pictures is at the operational point, means forcausing excess film tension in one direction whereby the force exertedon said film by said driving tooth is always in the same direction,-

and means for exerting normal pressure between said film and saidsprocket means and for relieving said pressure at the moment of transferof propulsion from one tooth to the next.

2. Means for moving a motion picture film past anoperational pointincluding sprocket means having a plurality of pairs of teeth adapted toengage perforations oppositely positioned at the two edges of said film,said pairs of teeth being so arranged that only one pair engages theperforations at a time, means for causing the film to be disengaged fromthe driving pair of teeth and engaged by the next succeeding pair 01'teeth when the framedine between pictures is at the operational point,means for causing excess film tension in she direction whereby the forceexerted on said film by said driving pair of teeth is always in the samedirection, and means for exerting normal pressure between said film andsaid sprocket means and for relieving said pressure at the moment oftransler of propulsion from one pair of teeth to the next.

3. Motion picture printing apparatus including a film movement controlsprocket provided with only one tooth per picture frame, means forcausing disengagement of one tooth and engagement of the next tooth atthe moment a picture frame line is in the path of the printing light,means for individually tensioning the printing and printed films wherebythe teeth of said sprocket always exert iorce'on said film in the samedirection, and means for exerting normal pressure between said films andsaid sprocket means and for relieving said pressure at the moment ofengager'nent and disengagement 0! said teeth with said film.

4. A printer for motion pictures including v sprocket means forimparting substantially continuous motion to both films, said sprocketmeans being provided with teeth having a pitch substantially equal tothe picture frame height, means for limiting the area being printed atany one time to a small fraction of the picture height, means forcausing disengagement of said teeth to occur when the frame line is atthe said limiting means, and means for exerting normal pressure betweensaid films and said sprocket means and for relieving said prwsure at themoment of engagement and disengagement of said teeth with said film.

5. Means for moving a motion picture film past an operational pointincluding sprocket means having retractable teeth only one of which isadapted to engage the film at a time, means for causing the film to bedisengaged from the driving tooth and engaged by the next succeedingtooth when the frame-line between pictures is at the operational point,means for causing excess film tension in one direction whereby the Iforce exerted on said film by said driving tooth is always in the samedirection, and means for exerting normal pressure between said film andsaid sprocket means and for relieving said pressure at the moment ortransfer of propulsion from one tooth to the next.

EDWARD W. KELIQGG.

